Extended Data Fig. 4 |. Codepletion of TRF2 and POT1A or POT1B result in LIG4-dependent end-to-end fusions.

a, Immunofluorescence staining for the pluripotency marker OCT4 (green) in Pot1b^−/− and Brd2^−/− ES cells. The percentage of positive cells is shown. Scale bar, 10 μm. b, Schematic of the Lig4 genomic locus, showing the predicted CRISPR–Cas9 cut site (scissors, red), and the sequence coding the essential R278 residue³² (blue). Sanger sequencing results showing successful gene editing of the Lig4 locus in four independent clones; the gRNA sequence is highlighted in red. c, Metaphases from ES cells of indicated genotypes. The percentage of telomeres engaging in telomere fusions are shown. In total, three independent experiments were performed. For a detailed summary of the data, see Supplementary Table 1 and Source Data for Extended Data Fig. 4.